The present invention relates to hydraulically operated lift systems for work surfaces and, more particularly, to such systems capable of keeping the work surface level during height adjustment.
Employers and workers in industrial environments are becoming increasingly aware of the need for ergonomic workstations. With cross-training of employees and multiple shifts operating in one factory, it is highly desirable that workstations in the industrial setting be adjustable to accommodate workers of various heights and to allow workers to alter their posture from time to time.
Various approaches to raising and leveling smaller workstations and desks include the use of multiple lift cylinders driven by a hydraulic drive. One such system is illustrated in U.S. Pat. No. 5,320,047 to Deurloo et al. The system is mounted on a desk and includes series-connected lift cylinders. A single hydraulic system drives the multiple cylinders. The desk may be re-leveled by extending the cylinders to the limits of their extension and then lowering the desk to a desired height. Another such system is manufactured and sold by Monarch Hydraulic, Inc., the assignee of the present application under the Dyna-Lift trademark. The system includes a plurality of leg cylinders--one for each leg--an a hand-crank actuated hydraulic system providing fluid to the cylinders.
The known systems do not provide sufficient strength and lifting capabilities to raise and lower large industrial workstations, which may weigh many tons, in a level fashion.